Parking availability information is beneficial to drivers who are looking for available parking spaces in a garage, or parking lot. Some garages or parking lots have sensors installed to monitor available parking spaces in the parking garages and parking lots, and to provide available parking space information to drivers by displaying the information at the entrance of the parking garages or the parking lots, or changing lights installed above the parking spaces, respectively. However, installation of the monitoring system is not only expensive but also time consuming. Accordingly, more efficient and less expensive way of monitoring parking spaces is needed.